1. Field of the Invention
This invention relates to a power feed through for vacuum electric furnaces wherein case formation on ferrous metals is provided by ions in the furnace and the protection of the power feed through against shorting.
2. Brief Description of the Prior Art
The process of case formation has been previously described in American Society for Metals, Metals Handbook, Vol. 2, commencing at p. 677, wherein is described the carburization of a surface of a ferrous work piece or ion nitriding of the surface of a work piece which provides a case which may be hardened as the case is formed or which may subsequently be hardened.
Examples of ion nitriding by ionization in a chamber of a nitrogen containing gas are shown in the U.S. Patents to Egan, U.S. Pat. No. 1,837,256, Berghaus et al., U.S. Pat. No. 2,837,654, Keller, U.S. Pat. No. 3,761,370 and Jones et al., U.S. Pat. Nos. 3,437,784 and 3,650,930.
The prior systems were particularly subject to arcing if the power input is high, which materially decreased the effectiveness of the process.
In the U.S. Patent to Jones et al., U.S. Pat. No. 3,437,784 a power supply is shown which is intended to limit arcing by limiting the current.
In utilizing ions for surface treatement in case formation materials sputtered from the work in the previously available equipment tended to build up on components in the furnace, including power feeders, causing arcing, excessive power requirements and shorting out of the electrical system.
The power feed through of our invention does not suffer from the problems encountered in previously available structures and has positive advantages.